Method and apparatus for cementing wells



Sept. 4, 1962 R. A, MALOTT METHOD AND APPARATUS FOR CEMENTING WELLSFiled March 22, 1960 FIG.

HIS AGENT ited binaires 3,052,296 METHOD AND APPARATUS FR CEMENTINGWELLS Raymond A. Malott, Fullerton, Calif., assigner to Sheil @ilCompany, New York, NX., a corporation of Delaware Filed Mar. 22, 1960,Ser. No. 16,693 4 Claims. (Cl. 166--22) This invention relates to amethod and apparatus for cementing wells and pertains more particularlyto a method and apparatus for forming a firm bond between cement andearth formation, eliminating the mud cake ring, channels and cavities.

In well drilling operations it is often necessary to place a quantity ofcement outside a well casing so as to close certain holes, slots orapertures which have been cut or formed in the wall of the well casing.Thus, for example, it may be necessary to cut, as by milling, alongitudinal slot in the well casing for `various purposes, such, foreX- ample, as for redrilling the well by side-tracking it to one side,etc. `It is therefore an object of the present invention to provide amethod and apparatus for plugging a window in a well casing prior toredrilling.

In redrilling a well by side-tracking, a window 30` feet or more inlength may be cut in the side wall of the well casing to permit drillingthrough the well casing at an angle to the original ywell borehole. IItis therefore another object of the present invention to provide a methodand apparatus for forming a good bond between a cement seal or plug andthe borehole formation to prevent the iedrilling bit from following thernud ring of the old ole.

In carrying out either of the above-described operations, it is commonto encounter a mud sheath on the wall of the borehole that wasoriginally deposited there by the circulation of a drilling `mud in theborehole during drilling operations and before a well casing was set.After a well casing has been positioned and sealed in a well, it isimpossible to circulate fluid on the outside of the casing in order towash the borehole wall. It is therefore another object of the presentinvention to provide a method and apparatus for hydraulically cleaning amud sheath off a borehole wall prior to cementing oper-ations (i.e.,through a perforated section of liner or casing).

During the producing life of a well it is quite common for water from alower `Water Zone to` cone upwardly around a well casing into theoil-producing zone so that large amounts of water are produced alongwith the oil. In order to eliminate some or all of the water coning, thelowermost perforations adjacent a producing Zone may be sealed off.Under normal presently known cementing methods it is diicult to form auidtight seal between the lwell casing and the formation outside theperfor-ations to be sealed. It is therefore a further object of thepresent invention to provide a method and apparatus for cementingthrough a perforated well casing or a well string to form an eifectiveseal outside the well casing to prevent water from channeling past theseal.

Still another object of the present invention is to provide a method andapparatus whereby the normal wall scraping operation is eliminated andat the same time 3,052,298 Patented Sept. 4, 1962 ice establishing a rmbond between a cement plug and the formation.

These and other objects of the present invention will be understood fromthe following description taken with reference to the drawing, wherein:

FIGURE l is a schematic view illustrating a well in longitudinalcross-section in which the method and apparatus of the present inventioncould be employed.

FIGURES 2 and 3 are additional alternative forms of a cementing tool tobe used in cementing operations in the well of FIGURE 1.

Referring to FIGURE 1 of the drawing, an oil )Well 10 is illustrated astraversing a Iwater zone 11 and an oil zone 12. A Well casing 13 hasbeen installed in the well 10 and sealed at the top as at 14 [and at thebottom as at 15 by cement which originally sealed ofi the waterproducing zone 11. However, during the production of the well, Water hasstarted to cone, as at 16, from the Water formation up into theoil-producing formation 12 so as to enter to bottom of the well casing13 through the perforations 17. The perforations =17 may be formed inthe bottom of the casing 113 in any suitable manner, as by shooting orcutting, or the perforated lower portion of. the well casing 13 mayoriginally consist of a well screen having slots of any suitable designand dimension therein.

The top 18 of the casing 13 may be open or closed, as desired, forcarrying out cementing operations. Positioned above the well casing is aderrick 20 having an operating door 21 on which normal well-drilling andcementing equipment, such, for example, as a rotary table 22 and `acement pump 23 may be placed. The discharge of the cement pump 23 isconnected by means of a conduit 24 to a string of pipe 25 which extendsdown intoI the well casing 13. The pipe string 25 may be either latubing string or, in some instances, may be the drill string which isemployed during drilling operations. FiXedly secured to the bottom ofthe pipe string 25 is a cementing sub 26 from which a plurality ofhorizontallydirected cement discharge ports extend. lIt has been foundthat Substantially horizontally-directed cement discharge or jettingports are needed in order to have cement i-mpinge on the formation withsufficient Velocity and momentum to create a good bond between .a cementplug or seal and the formation.

Another form of a cementing sub to be used in accordance with thepresent invention is shown in FIGURE 2. This cementing sub comprises ahollow body 30 threaded at the top, as at 31, for connection to thelower end of a drill suing. Secured to the bottom of the sub body 30 areblades 32 forming a drag bit. Extending downward from the chamber 33within the sub 30 are one or more `drilling mud discharge ports 34 whichmay be directed fat an angle so as to clean the blades 32, or which maybe directed downwardly against the bottom of a well borehole so that theentire sub forms a jet-type drag bit. Extending horizontally through theIwall of the sub body 30 are a plurality of cement discharge ports 35.These cement ports 35 are normally closed by pressure-fracturable discs36 or a sleeve. If during drilling operations it is desired to cementthrough the drill string without pulling the string and bit 32 to thesurface, a steel ball 37 may be dropped through the column of mud in thedrill string connected to the top of the sub 30 with the ball 37fin-ally coming to rest at the bottom of the chamber 33 where it closesthe mud discharge ports 34. Closure of the ports causes an immediatebuildup of pressure within the chamber 33 sufficient to fracture thediscs 36 so as to open the cement ports 35. Cementing operations maythen be carried out without pulling the drill string and bit to thesurface.

In FIGURE 3, a cementing sub 40 is shown as being connected `to acementing string 25 with a swivel joint 41 being connected into the sub40 so that the lower portion 42 is arranged to rotate on a verticalaxis. A plurality of horizontally-directed jet cementing nozzles 43 arearranged on the periphery of the rotatable portion 42 of the sub 40 sothat fluid jetting from the nozzel 43 causes the lower portion 42 of thesub 40 to spin on its vertical axis. All of the nozzles 43 are set at anangle to the radius in a horizontal plane to cause the lower portion 42of the sub 4G to rotate.

' In FIGURE 1, the well casing 13 is shown as having at a window 45 cut,as by milling or any other suitable method, in the side wall of the wellcasing 13. In such a situation it is desirable to form a hardconsolidated cement plug on the surface of the borehole outside thewindow 45 in the casing 13 prior to redrilling operations bysidetracking a bit. Since a mud sheath undoubtedly exists on the wall ofthe borehole opposite the window 45, a quantity of water is first pumpeddown through the pipe string 25 and out the jets 27 of the sub 26 toclean the wall of the borehole. The pipe string 25 would be rotatedrapidly as the pipe string 25 and its sub 26 were raised and/or loweredone or more times opposite the window 45. If desired, a quantity of sandmay be mixed with the water to give an abrasive effect to facilitateremoving the mud sheath from the wall of the borehole.

After sufficient water was jetted against the borehole wall opposite thewindow 45 to clean the formation, a cement slurry would then be pumpedby pump 23 through pipe string 25 and out the jet nozzles 27 so as toimpinge against the formation and also cause turbulence. A jet velocityof at least 100 feet per second should be employed so as to provide asatisfactory bond between the cement and the formation. Also, where -apermeable formation exists, the sand-cement slurry impinges on wall andremoves any mud cake allowing the cement to be exposed to hydrostaticdifferential across the face of the sand, resulting in rapid dehydrationof the cement slurry, a harder cement when set and a better bond. At thesame time the pipe string 25 and its sub 26 would be rotated, say, at aspeed of 100 revolutions per minute. Preferably, -the cement is sprayedon the borehole wall in a single vertical pass of the sub 26 over theentire length of the window 45 as the sub is pulled from the bottom tothe top of the window. However, in some situations it may be necessaryto run the sub down the length of the window again while continuing thejetting action to stir up the cement and form a better bond against thewall of the borehole. Afterwards, the pipe string 25 and the sub 26would be withdrawn from the well and the cement would be allowed to setup before resuming drilling operations.

The same procedure would be employed when it is desired to close thelower perforation 17 through which water from the water zone 11 isconing, as at 16'. Thus, by running the pipe string 25 down into thewell casing 13 until the jets 27 were opposite the lowermost perforation17, cement could be pumped down through the pipe string 25 and jettedout through nozzles 27 through the lowermost perforations 17 to form aseal between the well lcasing and the borehole wall opposite the cone16. It is only by jetting of a cement slurry that a suitable bond may beobtained in back of a perforated casing. Preferably in ,carrying outcementing operations in accordance with the present method the cementslurry contains from about -20% or more by weight of sand to furnish anabrasive action, directed velocity head, and turbulence to the cementingoperation. This eliminates the use of formation scratches which couldnot be used.

Alternatively, instead of rotating the pipe string 25 at relatively highspeeds during the cementing operation, the pipe string 25 may be heldstationary or substantially stationary if a rotatable cementing sub 40,as shown in FIG- URE 3, is employed. In such a case the lower portion 42of the cementing sub 4t? would rotate, thus eliminating any necessity ofrotating the cementing string 25.

In drilling wells it has been found that the borehole often enlarges, asat 48, to a diameter of a size so that it is impossible to set a packer.The apparatus of the present invention could be employed to set a plugof cement in this enlarged hole area by a spraying or jetting cementagainst the wall thereof at high velocities, say, 300 feet per second,in order to form a satisfactory bond. The plug would be allowed to setand drilled through so that a packer could be set at this level in theborehole. Additionally, if the well was drilled too deep, say, forexample, into a water sand, an excellent Water shut-off could beobtained by cementing the bottom of the borehole in accordance with themethod of the present invention.

I claim as my invention:

l. Apparatus for drilling and cementing a well, said apparatuscomprising a drag-type drill bit with a tubular body member having achamber formed therein, connector means at the upper end of said bodymember for connecting said body member to the lower end of a pipe stringin uid communication therewith, said body member being of a diameter topass longitudinally through a Well casing on the lower end of a pipestring and being rotatable therewith, a plurality of cement jettingdischarge ports extending horizontally and radially through the wall ofsaid body member for jetting a cement slurry horizontally against aborehole wall, a pressure disc normally closing each of said horizontaldischarge ports, normally open vertically-directed port means from saidchamber located below said radially extending discharge ports fordischarging -a uid downwardly out of said bit, said vertically-directedport means being adapted t0 be closed by an object dropped through apipe string and into the body member of said bit.

2. A method of cementing the annular space outside a well casing at apoint opposite at least one opening through the side wall of saidcasing, said method comprising lowering a uid jetting tool on the end ofa pipe string down through said casing to the opening in the casingwall, pumping a stream of well cementing uid down `said pipe string andjetting it horizontally at high velocity through said opening andagainst the previously cleaned borehole wall to establish an intimateuidtight bond thereon, continually discharging said horizontally jettingstream of well cementing iiuid while moving the pipe string and streamjetting therefrom over at least the entire opening in said well casing.

3. A method of cementing the annular space outside a well casing at apoint opposite at least one opening through the side wall of `saidcasing, said method comprising lowering a fluid jetting tool on the endof a pipe string down through said casing to the opening in the casingwall, pumping a nonsetting fluid down through said pipe string andjetting it horizontally through the opening in the casing wall andagainst the borehole wall at a velocity suficient to wash a mud sheathfrom the borehole wall, moving `said pipe string vertically andhorizontally while jetting over at least the entire Opening in said wellcasing, subsequently pumping a stream of well cementing Huid down saidpipe string and jetting it horizontally at high velocity through saidopening and against the previously cleaned borehole wall lto establishan intimate fluid-tight bond thereon, continually discharging saidhorizontally jetting stream of well-cementing fluid while moving thepipe string and stream jetting therefrom over at least the entireopening in said well casing.

aoeaooe 4. A method of `ceineriting a Well, said method cornprisinglowering a fluid jetting tool on the end of a pipe string down into awell to the level to oe cemented, pumping a nonsetting and formationcleaning fluid down through said pipe string and jetting it horizontallyagainst the borehole wall at a Velocity sufficient to Wash a mud Sheathfrom the borehole Wall, rotating said pipe string While moving saidjetting tool of said pipe string vertically over at least the entireportion of the borehole to be cemented, subsequently pumping a stream ofWellcementing fluid down said pipe string and jetting it horizontally athigh velocity against the previously cleanel borehole wail to establishan intimate fluidtight bond thereon, continually discharging saidhorizontally jetting stream of Well cementing uid While moving the pipestring and stream jetting therefrom over at least the entire area to becemented.

Referenees in the tile of this patent UNITED STATES PATENTS 1,276,536ergins Aug. 20, 1918 1,715,767 Le Flore June 4, 1929 1,912,578Halliburton June 6, 1933 2,971,389 Crowell Feb. 23, 1937 2,268,010 BaumDec. 30, 1941 2,315,496 Boynton Apr. 6, 1943 2,329,157 Frack Sept. 7,1943 2,771,141 Lewis Nov. 20, 1956 2,811,208 Eade Oct. 29, 1957

